title: Validity, intra- and inter-observer reliability of automated devices for the assessment of ankle brachial index using photo-plethysmography.
abstract: BACKGROUND
  Ankle-brachial-Index (ABI) measured by manual Dopplersonography is an easily assessable marker of global cardiovascular risk. The aim of this study was to establish novel photo-plethysmography (PPG)-based ABI assessments in an epidemiologic context and to compare its results with those of Doppler.
  
  
  METHODS
  Two devices for PPG-based ABI assessments (Vicorder, Vascular Explorer) were tested and compared against Doppler in 56 putatively healthy subjects. We determined acceptance, time requirements, agreement of repeat measurements, agreement with Doppler and intra- and inter-observer concordances for both devices and compared the results. Differences between cuff inflation- and deflation-based methods were also studied for Vascular Explorer.
  
  
  RESULTS
  Acceptance was similar for both devices but Vascular Explorer was more time consuming. Agreement of multiple measurements was moderate for both methods highlighting the importance of measurement replicates. Both automated devices showed significantly higher ABI compared to Doppler which can be traced back to higher brachial pressures (Vicorder) or higher ankle pressures (Vascular Explorer). This effect is more pronounced for Vascular Explorer but can be ameliorated using the deflation method of measurement. Intra-observer concordances were similar. Inter-observer concordance was non-significantly better for Vicorder.
  
  
  CONCLUSIONS
  Both devices proved to be feasible in epidemiologic studies, but compared to Doppler, do not constitute an advantage regarding time requirement and accuracy of ABI assessment. Since PPG-based ABI values are inflated compared to Doppler, it will be necessary to adjust Doppler-based cut-offs for risk stratification.
authors.affiliation: LIFE- Leipzig Research Center for Civilization Diseases, University of Leipzig, Leipzig, Germany. markus.scholz@imise.uni-leipzig.de.
authors.forename: Andrej
authors.initials: A
authors.lastname: Teren
authors.forename: Frank
authors.initials: F
authors.lastname: Beutner
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wirkner
authors.forename: Markus
authors.initials: M
authors.lastname: Loeffler
authors.forename: Markus
authors.initials: M
authors.lastname: Scholz
mesh_terms: D000368:Aged; D055109:Ankle Brachial Index / Q000379:methods / Q000592:standards*; D001331:Automation; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D017156:Photoplethysmography / Q000592:standards*; D010865:Pilot Projects; D018608:Ultrasonography, Doppler / Q000592:standards*